1. Field of the Invention
The present invention relates to a reference signal generator that can be used in an LCD backlight inverter and a PWM control circuit for LCD backlight, and more particularly, to a reference signal generator and a PWM control circuit capable of changing the frequency of a reference signal in a soft manner by inserting a frequency buffering interval when there is a change in the driving mode such as a change from initial driving to normal driving or a change from normal driving to protection driving.
2. Description of the Related Art
Generally, backlight inverters used in LCD (Liquid Crystal Display) TV sets or LCD monitors to which CCFLs (Cold Cathode Fluorescent Lamps) are applied include various protection circuits for protecting internal components.
In order to improve the quality of TV sets and monitors that have recently been developed, greater precision is require in the design of protection circuits. For example, in order to drive the CCFL (hereinafter referred to as a lamp) in the initial period, the protection circuit performs a function for lighting the lamp intensively at a high frequency that is higher than a normal frequency and lowering the frequency to the normal frequency at the time when the lamp is stabilized after an elapsed period of time.
In addition, when there is a problem in the operation of the lamp, the protection circuit performs a function of protecting an open part of the lamp and a transformer by operating the lamp at a higher frequency than that of normal operations.
However, in such a driving method, controlling a time interval for the lamp's higher frequency output in accordance with the lamp's specifications of the lamp and a driving current in the initial period may be demanding. In addition, there is a problem that internal components such as a lamp and a transformer may be damaged when an abrupt change from a high frequency to a low frequency or from a low frequency to a high frequency is made.